Dry reagent for testing



Patented Aug. 6,

UNITED STTES PATENT OFFiCE Denver Chemical Manufacturing Company,

New York, N. Y., a corporation of Colorado fio Drawing. ApplicationSeptember 3, 1937,

Serial No. 152,385

10 Claims.

This invention is a dry reagent for the direct and immediate testing,without external heating, for sugar, of bodily and other solutions, asblood and urine, particularly the latter. The ingredients in drycrystalline or powder form are mixed dry and in any order and theproduct is dry. It is in powder or tablet form ready, without heat otherthan that of the reactionresulting when a drop of the solution fallsupon it, to give the test on the instant.

The invention is based on the well-known Nylander test for sugar inurine by the reduction of a bismuth compound in the presence of acaustic alkali by sugar when present in the urine. Particles of themetal bismuth, freed in this way, being black are readily recognized andprove the presence of sugar. This, 1. e. the Nylander test, is a wettest, the ingredients in solution being mixed with the urine andsubjected to external heat. But it was natural to suppose that a drymixture of the bismuth compound and the caustic alkali would reactsimilarly with urine and would have the considerable advantages of dryreagents over solutions and, in fact, the dry mixture of a bismuth salt,bismuth subnitrate, and a caustic alkali, as sodium hydroxide, gives ablack color with a solution of dextrose, the heat evolved in themoistened powder by the reaction of sodium hydroxide and water beingsufficient to insure the reaction between the bismuth salt and sodiumhydroxide, without the boiling necessary in the wet test. However, thefact that such a dry test will work when the materials are freshly mixedis not enough to demonstrate the practicability of the test under theexacting conditions of general use, where individuals may make their ownunsupervised tests and where indefinitely old reagent-perhaps leftexposed in damp airmay be the medium for the urine test. On thecontrary, a reagent of this class to be of permanent practical valuemust be capable of giving immediate, sharply clear and conclusiveresults whenever it is desired to use the reagent, whatever the lapse oftime since it was made up. The test must be decisive and inability tomeet this critical requirement no doubt explains why this very simpletest never, became popular among physicians and laymen, in spite of itsdecided advantages over all other tests for sugar slowly in the presenceof air, light, moisture,

dust, etc., or any of them, so that after a. few months, three to sixunder ordinary conditions and less in hot countries or where the air ismoist, it cannot be relied upon-to give an immediate and certain test,and any blackening 5 which does in time occur may be due to the normalreducing power of the solution and not to sugar, so that the testbecomes inconclusive and the reagent useless. Speed, always andevidently desirable, thus becomes essential in testing low percentageglucose solutions. For example, in urine, the presence of certainnonsugar constituents (as a high percentage of uric acid or etc.) in thetested urine may give the sugar test in the absence of glucose, but itwould take five or ten minutes or more for the darkening to appear.

Furthermore, the bismuth compound-sodium hydroxide powder is extremelyhygroscopic, so that if it is left in the open air when the atmosphereis humid, a simple mixture of a bismuth compound and sodium hydroxidewould hardly resist more than half an hour or a'n hour without meltingand becoming useless, and even where this did not occur, inadvertentlyleaving the bottle or etc. containing the mixture open might result inmistaken reliance by the personmaking the test on results vitiated bythe condition of the reagent.

This is recognized in the German patent to Fornet, No. 592,923,published February 19, 1934, in which it is proposed to meet this defectby hermetically enclosing the powder in a capsule of hyaloid cellulose,a waterproof material, until pierced at the moment of use. 35

The present invention, when considered in its entirety lies in removingor minimizing the critical defects in the dry bismuth compoundcausticalkali mixture, viz., instability and the excessive hygroscopiccharacteristic, which have 40 been pointed out, and in speeding up thesugar reducing reaction and obtaining the maximum total heat productionin minimum time, and the sharpest test indication. This is done byadding other ingredients whose nature will hereinafter muth compound tobreak down and preventing the premature dehydrating action of the alkalihydroxide; The stabilizer here referred to is selected from the groupconsisting of lead and magnesium compounds. Bismuth is ordinarilyassociated with certain other metals, arsenic, antimony, iron, silver,lead, magnesium, present in metallic form as impurities, and I found itto be true that chemically pure bismuth subnitrate is not as stable asimpure bismuth subnitrate and that the like difference is still moreapparent in bismuth subcarbonate. By treating the bismuth with nitricacid, thus obtaining the metallic impurities as nitrates or other saltsand by a series of tests, I ascertained that the stabilizing effect inthe case of both the bismuth salts referred to was due to the lead andthe magnesium, the lead having more effect in this respect than themagnesium and both together having several times the effect of eitheralone, the criterion being the efiect of salts or other compounds ofthese metals when used with the respective bismuth salts on change ofcolor of the salt under conditions of tem.perature,-Iight, lapse oftime, etc., which would tend to cause change of color. Accordingly, Istabilized the mixture of the bismuth compound and caustic alkali by theaddition of minute proportions, large amounts not being necessary, withreference to the total weight of the reagent, in the case of eachstabilizing compound, of .05% by weight, more or less, of a compound(neutral in color) of each of these metals, which were found to have anegative catalytic efiect in the decomposition of bismuth salts or otherbismuth compounds. Magnesium oxide and magnesium carbonate I regard asthe best magnesium compounds for this use, both being very light,voluminous and flocculent. I have also used magnesium nitrate andmagnesium sulphate successfully, and I believe from my investigationsthat any other compound of magnesium would so far possess the requisitecharacteristics as to serve the purpose. I have tried with success eachof a number of lead compounds, among them lead nitrate, lead acetate,lead oxide' and lead sulphate and I am satisfied that it is the metal,lead, which gives the lead compound the stabilizing eflect, I believe,therefore, that any compound of lead; whether or not organic, notdisqualified by having a color sufilciently pronounced to obscure thetest, as in. case of red lead, lead sulphide, etc., would be acceptablefor this purpose and would be understood by a competent chemist to beso. As in the case of the bismuth salt, so in that of the mixture, thelead has a greater stabilizing effect than the magnesium and both thelead compound and the magnesium compound together several times theeffect of either alone. I have found further that these compounds areeffective in stabilizing bismuth compounds in a mixture of thischaracter against each and all of the adverse factors already named, andthat they are especially so in the case of bismuth compounds ofwater-free character to which further reference will be made in thecourse of this specification. Even if present in amounts largely inexcess of those named, they do not interfere with the normal reactionsof the bismuth compound and do not have any injurious effect on thenormal or abnormal constituents ,of urine. It is apparent that whenpresent in such amounts they should be anhydrous.

Proof of enhanced stability can be had only by tests at long intervalsof a given reagent.

Such prolonged tests are back of this invention and application. I haveascertained in this way that a powdered reagent of this nature, viz., amixture of bismuth oxychloride, sodium hydroxide, magnesium oxide andanhydrous lead nitrate! after being kept for a year, reacted in a testof urine immediately and with precision just as when it was newlycompounded. And there is no reason to suppose that it would not continueindefinitely in the like unimpaired condition. This illustrates oneaspect of my invention.

My belief as to the way in which these added compounds act is that thevoluminous magnesium compound has an effect at least partly mechanicaland that the lead compound and probably the magnesium compound alsoefiect the chemical operation in a manner which I do not altogetherunderstand, but which slows up, defers or prevents interaction of theingredients of the powder, particularly in the presence of moisture inthe pre-test powder, which is to say that the added compounds act asstabilizers and also as negative catalysts.

In referring above to the bismuth compounds, I have distinguishedbetween compounds having water associated with them as water of consti--tution or as water of crystallization, and anhydrous compounds ofbismuth which I describe as water-free and which do not yield water evenwhen heated. This is a distinction of importance and only bismuthcompounds of the latter character should be used in my reagent, since adry bismuth compound containing water in its molecule, such as bismuthsubnitrate and bismuth sbucarbonate, is readily attacked by sodium orpotassium hydroxide. This is illustrated by the fact shown by actualtests of a powder containing subcarbonate of bismuth,

CO3 (BiO) 2+1/ 2 (H20) and caustic alkali, which when first made up gavea successful test for glucose in urine, but after three months became amass oflumps capable when moistened of giving but very little heat anduseless for sugar tests except with high percentage solutions containing1% or more of sugar, whereas in urine .2% is pathological. Bismuth saltscontaining water thus become in time unfit for delicate sugar tests.

The water-free compound of bismuth which I find much the best for thispurpose is bismuth oxychloride, BiOCl, which in making the test ischanged to a fresh and therefore active oxide of bismuth, probablyB1203, which is readily reduced by sugar in the urine (or othersolution) to metallic bismuth or other bismuth indication. Bismuthoxychloride is a very fine, light powder, not hygroscopic at all, andwater free, all of which characteristics are of special advantage in myreagent. It is a white powder. Bismuth chloride, 31011, on the contraryis highly hygroscopic, and though it is anhydrous, its use is excludedby practical considerations. It must not be inferred, however, thatbismuth oxide, BizOz, or other bismuth oxide, is suitable for useinitially in a sugar testing reagent. Although this compound is entirelyfree of water, it has a very unfavorable influence on the sensitivenessand speed of the reaction. And this is true also where tl aoxide isformed slowly by the breaking down of a different compound of bismuth ina dry testing reagent of this class. In order to be quickly and easilyreduced to black metallic bismuth, the bismuth oxide must be as freshlyprepared as possible, ideally at the instant of performing the test.Oxychloride of bismuth and other anhydrous bismuth salts, as bismuthsulplate, borate, and phosphate act in this'way producing a fresh andhighly reactive oxide, the reducing action of the sugar being much moreenergetic under these conditions, this enhanced reactivity andreducibility being a common property of metallic oxides at the moment oftheir formation.

The other characteristic of a dry reagent of this classwhich'incapacitates it for safe Practical use in all handsindiscriminately'is that it is extremely hygroscopic. This, by addingmoisture, increases its natural instability and creates conditionsunfavorable to the heat producing reaction which is the basis of thetest, as well as to the reactions resulting in the reduction of thebismuth compound. While my reagent is not completely non-hygroscopic, Ihave been able to reduce its hygroscopic character very materially,

so that the reagent can be exposed to the open air for a substantialtime (twenty-four hours in dry air) without disqualifying it for use fortesting purposes. The reagent would react thereafter as well, if not soquickly as before. I have found that sodium silicate or potassiumsilicate, when added in substantial amount to the bismuth salt-causticalkali powder (with or without a further stabilizer), both have thisbeneficial effect, although themselves hygroscopic, and act also inother vital ways about to be stated. They both have capillary structureand are soluble. By capillary structureis meant that the ingredient ischaracterized throughout its mass by a multiplicity of capillaries, i.e. capillary pores, canals or crevices. The action is understood to beby interfacial tension. Both the dry silicates named may be obtained inthe open market. Each is understood to act in four ways ,(1) It makesthe mixture less hygroscopic. (2) It lessens the contact or intimacy ofthe contact, between the other ingredients, thus by mechanical dilutiondiminishing also their reaction while awaiting use and furtherstabilizing the powder. (3) It is a reaction-accelerator. It distributesthe solution in making the test, 1. e.,- having capillary structure itenables the small drop of solution (urine or etc.), by which it iscapable of being wet, to penetrate immediately by a multiplicity ofpaths the entire mass of. the small portion of powder used in the test(about 0.2 of a gram) permeating on the instant every particle and thuscarrying out the reaction at the same time in every part of the massthereby attaining in the least time the highest temperature that can beobtained with a given amount of powder, and (4) giving the sharpestdefinition in the test indication as Well as the quickest.

The added ingredient is a material compatible with the reaction orreactions which the test involves and substantially inert to the othermaterials of the mixture in its substantially dry state. This means thatthe material is not an oxidizing agent,or a reducing agent or acidic incharacter. This fact assists in the performance of functions (1) and(2).

In performing function (3) the ingredient overcomes, by virtue of itscapillary structure, the fundamental difficulty inherent in the simplebismuth compound-caustic soda mixture due to insolubility of the bismuthcompound and of and are insoluble as well and so present a sort of wallor insulation localizing the reaction bydelaying or preventing progressof the moisture of the solution to the non-proximate particles of thepowder, thereby reducing the extent of the reaction, the promptness of.it and the amount and speed of heat production frequently below thepoint essential to the testjso that a negative result is meaningless andthe reagent cannot be relied on. The addition of this compound having acapillary structure substitutes positive values at each of thesev pointsfor the negative disadvantages inherent in the bismuth salt-alkalimixture, and assists in making it safe to rely on the reagent. Each ofthe functions above enumera'ted contributes to the efficacy of thereagent and all are important. As to function (4) This is the directconsequence of the realization of function (3), but there is a furtherincrease or accentuation of sharpness of the test indication believed tobe due to the power of the soluble sodium silicate or potassium silicateto protect colloids against coagulation. This preserves the very intensecolor characteristic found even in very small quantities of colloids, asagainst absence or faintness of color in the same quantities whencoagulated and no longer colloidal. Prevention of coagulation of themetallic bismuth, which at the instant of its formation-by reduction ofits oxide by sugar is a colloid, is thus insured so that the test isexceptionally sharp even compound or the magnesium compound or both ofthem.

Soluble silicates, in particular sodium and potassium silicates, arepreferred to other materials since they can perform all four of thelisted functions very effectively and give the most rapid and sharpesttest of any material or compound of which applicant is aware, being inthese respects notably superior.

Up to this point little has been said as to the relative amounts inwhich the principal ingredients are to be used. The fact is that this isdictated in a general way by the nature of. the ingredients and by thetask to be performed. The

percentages of the respective materials will be reagent is made up to besensitive to not less than about 0.1%. This is sufficiently sensitivefor the sugar test, but not so sensitive as to give the black sugar testindication immediately in response to non-sugar constituents havingreducing power. Putting in more of the bismuth salt which beinginsoluble tends to cover the black in the test makes the reagent lesssensitive, as is necessary in testing blood which normally hasapproximately 0.1% of. sugar, so that the reagent, in this case, shouldnot respond to so little as 0.1% of sugar. It will be apparent that incompounding the reagent account must always be taken of the insolubilityof the bismuth compound, which if present in undue amount tends to coverthe black particles of the free bismuth and so obscure the test. Accountmust also be taken of the amount of. any other insoluble ingredient, andthe total insoluble content of the 'reagent must be kept below the pointat which it would obscure the test indication to an extentnotpermissible for the particular solution to be tested. Whether. or notspecified in particular claims, it is to be understood, also, thatmaterials which by their color and amount would obscure the test areexcluded.

Proportions by weight which I have found in actual practice to beeflective in the dry reagent for a sugar test of urine are as follows:bismuth salt (bismuth oxychloride) 12.5%; caustic soda 56.5%; magnesiumoxide or magnesium carbonate 0.05%; nitrate of. lead 0.05%; and thebalance sodium silicate. Testing reagent of this composition andproportions is still fully effective and reliable many months after itwas made up.

It is to be understood that the proportions just given, while suggestiveand while indorsed by experience are approximate and are not to be takenas invariable, but are to be modified according to the nature of theparticular solution to be tested and other special circumstances as willbe apparent to a chemist. The ingredients are most readily mixed in theform of powder and in any order. None of the ingredients is wet; all aredry and not too coarse in the case of. the silicate or capillaryingredient to have a capillary action,

and not too coarse to lose the power to counteract hygroscopiccharacteristic of the mixture. N0 difiiculty is experienced on thisscore, however, since the dry sodium silicate and the dry potassiumsilicate on sale in the open market have capillary structure and aresuitable for applicants purpose. Compacted into tablets the reagent isless sensitive, and its use as a powder is as a rule preferred.

In making the urine test the reagent (about .2 of a gram), whenmoistened with a drop of urine, acts instantly, in one or two seconds,that is, and marks a decided advance in that important respect, therapidity of the test excluding as the cause of. the indicationeverything but sugar. The reaction is very sharp giving under 0.1% ofsugar only a slight gray color whereas with 0.2% a strong black colorwhich never fails to appear and which is recognized without difilcultyor possibility of error is developed. The reagent is stable and wouldnot give any yellow, gray or black coloration, other than the test.

I claim:

1. A dry reagent for testing urine for sugar adapted to react to a dropof urine to test it without the application of heat other than that ofthe reaction itselfQcontaining a water-free bismuth salt, causticalkali, and sodium silicate.

2. A dry reagent for testing urine for sugar adapted to react to a dropof urine to test it without the application of heat other than that o;the reaction itself, containing a water-tree bismuth salt, causticalkali, and potassium silicate.

3. A dry reagent for drop contact testing of solutions for sugarcomprising a mixture containing an anhydrous bismuth salt, causticalkali, and a lead compound and a magnesium compound both neutral incolor and serving as sta bilizers for the mixture prior to use.

4. A dry reagent for drop contact testing of solutions for sugarcomprising a mixture containing an anhydrous salt of. bismuth, causticalkali, and a mixture-stabilizing magnesium compound.

5. A dry reagent for testing urine for sugar, on contact without theapplication of external heat, containing bismuth oxychloride, andcaustic alkali, a magnesium compound selected from the group consistingof the oxide and the carbonate and nitrate of lead, and sodium silicate.

6. A dry reagent for drop contact testing of. solutions for sugar,comprising a mixture containing an anhydrous bismuth salt, causticalkali, a stabilizer for said mixture selected from the group consistingof lead and magnesium compounds, and a soluble silicate.

7. A dry reagent for drop contact testing of solutions for sugar,comprising a mixture containing an anhydrous bismuth salt, causticalkali, and soluble silicate.

8. A dry reagent for testing urine for sugar containing an anhydrousbismuth salt, caustic alkali and a magnesium compound selected from thegroup consisting of the oxide and the carbonate, soluble silicate, and astabilizer being a lead compound neutral in color.

9. A dry reagent of the class stated adapted to give the test on dropcontact comprising a mixture containing a bismuth compound and causticalkali, a magnesium compound and a lead compound, and soluble silicatein relatively large amount.

10. A dry reagent of the class adapted to give the sugar test onldropcontact comprising a mixture containing an anhydrous bismuth salt andcaustic alkali, a stabilizer for the mixture, and a soluble silicateneutral in color and having capillary structure, whereby the moisturerapidly penetrates the mass permeating its particles and a sharplydefined test indication results.

.ALEXANDER GALAT.

